Immune complexes (IC's) are formed in a person when an antibody binds to an antigen. Generally such immune complexes formed in small amounts in healthy persons are effectively removed by the person's mononuclear phagocytic system (MPS). However, in diseased persons, the immune complexes are formed in greater amounts and the diseased person's MPS is not able to effectively remove the IC's from the diseased person's plasma resulting in an overload in the person's system. As a result of an overload of these immune complexes in the person's circulation system, these immune complexes are deposited in the diseased person's tissue causing immunopathological reactions at various tissue sites.
The kind of immune complexes present in a person having a disease depend on the phase of the person's disease. There are two types of complexes.
In the initial phase of a disease, the amount of immune complex formed is excess antibody immune complexes and comprises antigen and antibody molecules. These types of complexes, apparently more insoluble, have a tendency to be deposited at various sites in the tissue. This type of IC's are also formed in situ at tissue sites and as noted above, cause immunopathological reactions.
During a late phase of disease, due to increased number of antigen molecules, a second type of immune complex comprising excess antigens and an antibody and a complement protein (a group of proteins present in the blood) is formed. These types of immune complexes are more soluble and circulate for a longer time in the blood. The immune complexes activate complement cascade, leads to formation of C5-C9 esterase activity that results in increased vascular permeability and release of vasoactive amines. It is desired to remove both types of IC's.
The removal of circulating immune complexes in Systemic Lupus Erythromatosus patients by C1q Immunoadsorption chromatography has provided beneficial effect to these patients.